US 2010/0061596 A1 discloses method of determining a similarity with a portion of a physiological motion, the method comprising the steps of:
obtaining a first image of an object;
obtaining a second image of the object;
determining a level of similarity between the first and second images; and
correlating the determined level of similarity between the first and second images with a portion of the physiological motion.
The document further discloses several refinements of the method. Although considerable progress in the field of computing performance has been made, it is still a challenge to provide for instant image recognition and image processing enabling immediate, so to say, on-line detection of desired vital signals. This applies in particular to mobile device applications commonly lacking of sufficient computing power.
A further challenge may arise from several constraints which must be taken into account for the detection of the desired signals. Commonly, detection quality can be enhanced by applying obtrusive measurement, e.g., when applying markers to an object to be monitored. Still, however, obtrusive measurement, e.g. utilizing belts or sensors attached to a person's body, is considered uncomfortable and unpleasant.
Further, as the recorded data, such as captured reflected or emitted electromagnetic radiation, especially recorded image frames, always comprises, beside of the desired signal to be extracted therefrom, still further signal components deriving from overall disturbances, by way of example, such as noise due to changing luminance conditions or a disturbing motion of observed objects, a detailed precise extraction of the desired signals still poses major challenges for the processing of such data. Furthermore, object motion related signals are, so to say, attenuated in case the object of interest is covered, e.g. by clothes or even blankets.
After all, this applies in particular when amplitudes and/or nominal values of disturbing signal components are much larger than amplitudes and/or nominal values of desired signal components to be extracted. Potentially, the magnitude of difference between the respective components can be expected to even comprise several orders.
A possible approach to this challenge may be directed to providing well-prepared and steady ambient conditions when capturing a signal of interest in which the desired signal component is embedded so as to minimize disturbing signal components overlaying the signal. However, such laboratory conditions cannot be transferred to everyday field applications as high efforts and preparation work would be necessary therefor.
The required preparation might comprise, by way of example, installation and orientation of several standard light sources and, moreover, measures for fixation of the object to be observed in order to avoid disturbing motions responsible for an even larger noise level. However, these measures are considered unlikely to be applied for everyday applications, e.g. ambulant or clinical patient monitoring, or even for lifestyle applications like sporting and fitness monitoring.